Structural adhesives are a good alternative to other mechanical techniques for binding two materials together, such as metals or plastics. This is because the force distribution is better with bonding than when alternative techniques such as riveting or welding are used. In addition, the use of bonding often makes it possible to work more rapidly, and also has the advantage of providing better insulation against external elements (dust, moisture) than the mechanical technologies.
Structural adhesives are formed from two components: a composition containing the curing agent (based on acrylate or on methacrylate) and a catalyst for curing and setting the adhesive. These two components are stored in two different compartments and are mixed at the time of application of the adhesive. This catalyst is a free-radical polymerization initiator, in particular based on peroxide, and is well known in the art.
The compositions containing the curing agent also contain other elements, such as a cure accelerator, a rheology modifier or an adhesion promoter.
The cure accelerator serves to promote curing and hardening of the adhesive when the catalyst is added. The use of tertiary amines, preferably aromatic tertiary amines, such as dimethyl-para-toluidine (DMPT), and/or 2,2′-(p-tolylimino)diethanol or dimethylaniline (DMA), is known in the art.
These cure accelerators make it possible to obtain a high degree of curing of the adhesive and to improve its mechanical performance levels and its strength in a difficult environment.
Such tertiary amines are in particular described in U.S. Pat. No. 4,223,115 and EP 894 119.